Details of The Pictou Highlanders were called out on service on 26 August 1939 and then placed on active service on 1 September 1939 as The Pictou Highlanders, Canadian Active Service Force (Details), for local protection duties. The details called out on active service disbanded on 31 December 1940.[3]
The regiment mobilized the 1st Battalion, The Pictou Highlanders, CASF for active service on 1 January 1941. It served in Newfoundland from March to August 1943 in a home defence role as part of Atlantic Command. In September 1943, one company was despatched to the Bahamas, where it performed garrison duty until 28 March 1946. The battalion was disbanded on 30 April 1946.
On 10 September 1942, a sub-component of the regiment, designated Special Infantry Company (Pictou Highlanders), CASF, was mobilized for active service. It served in Bermuda on garrison duty from 12 November 1942 to 1 April 1946. The company disbanded on 30 April 1946.
Details of The North Nova Scotia Highlanders were called out on service on 26 August 1939 and then placed on active service on 1 September 1939 as The North Nova Scotia Highlanders (Machine Gun), CASF (Details), for local protection duties. The details called out on active service were disbanded on 31 December 1940.[3]
The regiment subsequently mobilized The North Nova Scotia Highlanders, CASF for active service on 24 May 1940. It was redesignated as the 1st Battalion, The North Nova Scotia Highlanders, CASF on 7 November 1940. It embarked for Great Britain on 18 July 1941. On D-Day, 6 June 1944, it landed in Normandy as part of the 9th Infantry Brigade, 3rd Canadian Infantry Division, and it continued to fight in North-West Europe until the end of the war. The overseas battalion disbanded on 15 January 1946.
On 1 June 1945, the regiment mobilized the 3rd Battalion, The North Nova Scotia Highlanders, Canadian Infantry Corps, Canadian Army Occupation Force for service with the Canadian Army Occupation Force in Germany. The battalion disbanded on 1 May 1946